1. Field of the Invention
The present invention relates to a magnetic copying method and apparatus and, more particularly, to a novel magnetic copying method and apparatus in which a number of copies of many originals are easily obtained.
2. Description of the Prior Art
In order to obtain plural copies of numerous pages of originals, a printing system, such as an offset printing system and a high-speed electrographic system, are employed.
In the offset printing system, printing plates are formed individually for each page of a set of originals, and these plates are used to provide the respective prints. Accordingly, this system is disadvantageous because it takes a relatively long time to form printing plates, i.e., it is difficult to accomplish a printing operation quickly. In addition, one copy of a set of originals is obtained after all of the originals have been printed. Therefore, the system is not suitable for cases in which it is required to obtain the copy of the original quickly.
In the electrographic system, copies of a set of originals (consisting of a plurality of pages) can be obtained one-by-one. However, in order to obtain a number of copies of the set of originals, it is necessary to expose each original repeatedly to light and to use an intricate original circulating device.
A method may be considered in which picture data to be printed are stored in an electrical memory means which comprises a semiconductor or magnetic substance, and the picture data, thus stored, can be read out for every page so that copies of the set of originals can be made set-by-set. However, in general, the picture data memory capacity is required to be large, and it is therefore required to use a combination of memories which are large in capacity and low in price. In order to meet this requirement, a magnetic tape is employed.
In the case in which a magnetic tape is used as the memory, since the picture data are time series signals which have been suitably compressed, it is necessary to use an intricate decoding device in order to convert the signals into pictures. Therefore, the use of the magnetic tape as the memory is disadvantageous in that the copying device using the picture memory is bulky and relatively expensive.